Road vehicles -- Passenger-car and trailer combinations -- Lateral stability test

ISO 9815:2010 specifies a lateral stability test for passenger-car and trailer combinations. It is applicable to passenger cars in accordance with ISO 3833, and also to light trucks, and their trailer combinations. The lateral stability test determines the damping characteristic of the yaw oscillation of such towing-vehicle–trailer combinations excited by a defined steering impulse. The combination is initially driven in a steady-state, straight-ahead driving condition. Oscillation of the vehicle is then initiated by the application of a single impulse of steering, followed by a period in which steering is held fixed and the oscillation of the combination is allowed to damp out. Testing is conducted at several constant speeds. Where non-periodic instability is of interest, a steady-state circular test is specified.

Véhicules routiers -- Ensembles voiture particulière et remorque -- Essai de stabilité latérale

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Published
Publication Date
29-Apr-2010
Current Stage
9092 - International Standard to be revised
Start Date
21-Jun-2021
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INTERNATIONAL ISO
STANDARD 9815
Third edition
2010-05-01
Road vehicles — Passenger-car and
trailer combinations — Lateral stability
test
Véhicules routiers — Ensembles voiture particulière et remorque —
Essai de stabilité latérale
Reference number
ISO 9815:2010(E)
ISO 2010
---------------------- Page: 1 ----------------------
ISO 9815:2010(E)
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ii © ISO 2010 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 9815:2010(E)
Contents Page

Foreword ............................................................................................................................................................iv

Introduction.........................................................................................................................................................v

1 Scope......................................................................................................................................................1

2 Normative references............................................................................................................................1

3 Terms, definitions and symbols ..........................................................................................................1

4 Measurement variables.........................................................................................................................2

5 General conditions ................................................................................................................................2

5.1 Compliance ............................................................................................................................................2

5.2 Measuring equipment ...........................................................................................................................2

5.3 Test track................................................................................................................................................3

5.4 Wind velocity .........................................................................................................................................3

5.5 Loading conditions ...............................................................................................................................3

6 Test method ...........................................................................................................................................5

6.1 General ...................................................................................................................................................5

6.2 Test runs.................................................................................................................................................5

7 Data analysis..........................................................................................................................................7

7.1 General ...................................................................................................................................................7

7.2 Individual test runs................................................................................................................................8

7.3 Zero-damping speed ...........................................................................................................................10

7.4 Reference-damping speed..................................................................................................................10

7.5 Reference-speed damping..................................................................................................................11

8 Data presentation ................................................................................................................................11

8.1 General data.........................................................................................................................................11

8.2 Test conditions ....................................................................................................................................11

8.3 Results..................................................................................................................................................11

Annex A (normative) Test report — General data (supplement to ISO 15037-1:2006, Annex A).................12

Annex B (normative) Test results....................................................................................................................15

Annex C (normative) Steady-state behaviour................................................................................................16

Bibliography......................................................................................................................................................17

© ISO 2010 – All rights reserved iii
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ISO 9815:2010(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies

(ISO member bodies). The work of preparing International Standards is normally carried out through ISO

technical committees. Each member body interested in a subject for which a technical committee has been

established has the right to be represented on that committee. International organizations, governmental and

non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the

International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 9815 was prepared by Technical Committee ISO/TC 22, Road vehicles, Subcommittee SC 9, Vehicle

dynamics and road-holding ability.

This third edition cancels and replaces the second edition (ISO 9815:2003), which has been technically

revised.
iv © ISO 2010 – All rights reserved
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ISO 9815:2010(E)
Introduction

The main purpose of this International Standard is to provide repeatable and discriminatory test results.

The dynamic behaviour of a road vehicle is a very important aspect of active vehicle safety. Any given vehicle,

together with its driver and the prevailing environment, constitutes a closed-loop system that is unique. The

task of evaluating the dynamic behaviour is therefore very difficult since the significant interaction of these

driver-vehicle-environment elements are each complex in themselves. A complete and accurate description of

the behaviour of the road vehicle must necessarily involve information obtained from a number of different

tests.

Since this test method quantifies only one small part of the complete vehicle handling characteristics, the

results of these tests can only be considered significant for a correspondingly small part of the overall dynamic

behaviour.

Moreover, insufficient knowledge is available concerning the relationship between overall vehicle dynamic

properties and accident avoidance. A substantial amount of work is necessary to acquire sufficient and

reliable data on the correlation between accident avoidance and vehicle dynamic properties in general and the

results of these tests in particular. Consequently, any application of this test method for regulation purposes

requires proven correlation between test results and accident statistics.
© ISO 2010 – All rights reserved v
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INTERNATIONAL STANDARD ISO 9815:2010(E)
Road vehicles — Passenger-car and trailer combinations —
Lateral stability test
1 Scope

This International Standard specifies a lateral stability test for passenger-car and trailer combinations. It is

applicable to passenger cars in accordance with ISO 3833, and also to light trucks, and their trailer

combinations.

The lateral stability test determines the damping characteristic of the yaw oscillation of such towing-vehicle–

trailer combinations excited by a defined steering impulse. The combination is initially driven in a steady-state,

straight-ahead driving condition. Oscillation of the vehicle is then initiated by the application of a single

impulse of steering, followed by a period in which steering is held fixed and the oscillation of the combination

is allowed to damp out. Testing is conducted at several constant speeds. Where non-periodic instability is of

interest, a steady-state circular test is specified.
2 Normative references

The following referenced documents are indispensable for the application of this document. For dated

references, only the edition cited applies. For undated references, the latest edition of the referenced

document (including any amendments) applies.
ISO 1176, Road vehicles — Masses — Vocabulary and codes
ISO 2416, Passenger cars — Mass distribution
ISO 3833, Road vehicles — Types — Terms and definitions

ISO 4138:2004, Passenger cars — Steady-state circular driving behaviour — Open-loop test methods

ISO 8855, Road vehicles — Vehicle dynamics and road-holding ability — Vocabulary

ISO 15037-1:2006, Road vehicles — Vehicle dynamics test methods — Part 1: General conditions for

passenger cars
3 Terms, definitions and symbols

For the purposes of this document, the terms, definitions and symbols given in ISO 3833, ISO 8855 and the

following apply.
3.1
yaw articulation angle

angle of the X axis relative to the X axis, i.e. angle between the X axes of each of the two units, with the

C T

polarity determined by the rotation of the towing vehicle relative to the trailer

NOTE The letters “C” and “T” are used as subscripts to distinguish between variables associated with the towing

vehicle (car or light truck) and the trailer, respectively. For example, the longitudinal axis of the intermediate axis system of

the towing vehicle is designated as X , and the lateral acceleration of the trailer is designated as a .

C YT
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ISO 9815:2010(E)
3.2
mean gradient (of the test track)

change in elevation of the track surface between two points along the path of the vehicle divided by the

horizontal distance between those points, where the two points are those that define, as closely as is

practicable, that segment of the track travelled by the test vehicle between the times t and t , respectively

2 ∆ψn
For t and t , see 6.2.2 and 7.2.3, respectively.
2 ∆ψn

NOTE This gradient is dimensionless and is positive for a test vehicle travelling uphill and negative for a test vehicle

travelling downhill.
4 Measurement variables
When performing this test procedure, the following shall be measured:
⎯ steering-wheel angle, δ ,
⎯ longitudinal velocity of the towing vehicle, v ,
⎯ lateral acceleration of the trailer, a ,
⎯ yaw articulation angle between towing vehicle and trailer, ∆ψ.
The following should be measured:
⎯ yaw velocity of the towing vehicle, ;
⎯ yaw velocity of the trailer, .
NOTE These variables are not intended to comprise a complete list.
5 General conditions
5.1 Compliance

The general conditions of the test shall be in accordance with ISO 15037-1, with the additions and exceptions

given in this clause.
5.2 Measuring equipment

The measurement variables given in Clause 4 shall be monitored using appropriate transducers. The

requirements of ISO 15037-1 regarding measurement and recording equipment shall be applied to both

towing vehicle and trailer. Typical operating ranges and recommended maximum errors for variables not

considered by ISO 15037-1 are given in Table 1.

A steering-wheel stop or marking may be used. The use of a steering machine is optional.

Table 1 — Variables, operating ranges and recommended maximum errors —
Addendum to ISO 15037-1:2006, Table 1
Recommended maximum error
Variable Typical operating range
(of combined transducer/recorder system)
Articulation angle ± 20° ± 0,2°
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ISO 9815:2010(E)
5.3 Test track

In addition to the test track requirements of ISO 15037-1, the mean gradient of the test track along the path of

the vehicle, G , shall be within the range ± 0,01. G shall be recorded for each test run. See 6.2.1 and 7.2.1 for

related requirements. In addition, the test surface shall be maintained over a track with a minimum width of

8 m. An increased run-off area should be provided in addition to the specified test surface.

Inasmuch as yaw damping of articulated vehicles is known to be sensitive to the longitudinal slope of the test

track, the test should be conducted in both directions whenever G approaches the allowed maximum.

5.4 Wind velocity

Wind velocity shall be in accordance with ISO 15037-1 and, in addition, should not exceed 2,5 m/s.

5.5 Loading conditions
5.5.1 Towing vehicle

The total mass of the towing vehicle shall consist of the complete vehicle kerb mass (ISO 1176, code

ISO-M06) plus driver and instrumentation (combined mass should not exceed 150 kg). The location of the

instrumentation shall be such as to minimize its effect on the yaw moment of inertia of the towing vehicle.

The tests should be repeated at a maximum loading condition of the towing vehicle or at other loading

conditions of interest or all these. For the maximum loading condition, the total mass of a fully laden vehicle

shall consist of the complete vehicle kerb mass plus 68 kg for each seat in the passenger compartment, with

the static load at the coupling ball and the remaining maximum luggage mass equally distributed over the

luggage compartment in accordance with ISO 2416. Loading of the passenger compartment shall be such that

the actual wheel loads are equal to those obtained by loading each seat with 68 kg in accordance with

ISO 2416. The mass of instrumentation shall be included in the vehicle mass. Care shall be taken to ensure

that the moments of inertia are representative of the loading conditions of the vehicle in normal use.

The total mass of the fully laden towing vehicle, including the equivalent mass of the static load at the coupling

ball, shall not exceed the maximum design total mass (ISO 1176, code ISO-MO7), nor shall the front and rear

axle loads exceed their respective maximum design values with the load applied at the coupling ball. If a load-

distributing coupling is used, these axle loads should be assessed after engagement of the load-distributing

mechanisms (see 5.5.4), except where this is counter to the recommendations of the manufacturer of the

towing vehicle.
5.5.2 Trailer

The trailer shall be loaded to its maximum authorized total mass (ISO 1176, code ISO-M08) or until the

maximum design mass of vehicle combination (ISO 1176, code ISO-M18) is reached, whichever is the lesser

of the two masses. If the type of trailer allows various load distributions, the load shall be distributed in such a

way as to produce realistic and representative values of the yaw moment of inertia, centre-of-gravity height

and the static load at the coupling ball (see 5.5.3).
Optionally, tests may also be carried out with any other towed mass of interest.

The mass, centre-of-gravity position and yaw moment of inertia of the trailer as tested shall be measured and

noted in the general data (see Annex A). Alternatively, a description of the loading condition, adequate to

reproduce these properties with reasonable accuracy, shall be provided.
5.5.3 Static load on the coupling ball

Tests shall be carried out with the maximum permissible static load on the coupling ball as determined by the

maximum coupling load allowable for the towing vehicle, the trailer or the coupling itself, whichever is the

smallest. However, it is necessary to reduce further the static load on the coupling ball if it causes the load on

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ISO 9815:2010(E)

the rear axle of the towing vehicle to exceed the maximum design load as specified by the manufacturer of the

towing vehicle. Unless it is counter to the recommendations of that manufacturer, the rear-axle load is to be

assessed after the engagement of any load-distributing mechanism at the coupling.

The fraction of the weight of the trailer carried as static load on the hitch has an important influence on the

yaw damping of the vehicle combination. Typically, damping decreases as static load on the hitch decreases.

Therefore, tests should also be carried out with the minimum permissible static load at the coupling ball (see

[1])
ISO/TR 4114 .
5.5.4 Adjustment of load-distributing coupling mechanisms

When trailer mass is large, load-distributing couplings are often used to restore the pitch angle exhibited by

the towing vehicle prior to the application of a static load on the coupling. The addition of this moment

redistributes some of the coupling static load from the rear tyres to the front tyres of the towing vehicle and the

trailer tyres. This increases the articulation-angle damping but reduces the understeer of the towing vehicle

with lateral acceleration.

The load-distributing coupling often includes a mechanism for adding articulation-angle damping. The coupling

and auxiliary friction devices should be installed and adjusted according to the towing vehicle, trailer and

coupling manufacturers' recommendations.

In the absence of manufacturers' recommendations for the use of load-distributing coupling, the following

procedure should be followed. Prior to the attachment of the trailer, measure the vertical distance from points

on the vehicle body to the ground at the centre lines of the front and rear axles of the towing vehicle, with the

vehicle loaded as intended for testing. After attaching the trailer, adjust the coupling moment such that the

resulting overall changes in these two vertical distances are the same within 10 mm.

If recommendations for static loading conditions are not available for the load-distributing coupling, static load

can be based upon the recommendation of Reference [2], which is that coupling load should be 8,4 % of the

weight of the towing vehicle.

NOTE With multi-axle trailers, the force required to support the tongue may increase as the height of the tongue is

increased. As a result, proper set-up of the static load on the coupling ball and coupling moment can be an iterative

process.

The coupling moment should be recorded for the test configuration. For this, the front and rear axle loads of

the towing vehicle should be measured once without the trailer attached (to determine the weight of the towing

vehicle) and once with the trailer attached and the load-distributing coupling adjusted. The axle loads shall be

measured with the trailer and towing vehicle on a flat surface. If the contact patches of the towing-vehicle and

trailer tyres are not in the same plane, the coupling moment is altered.

The moment due to a load-distributing coupling, M , can be calculated as follows:

Yeq
M=+Fl()e+F (e)−mg(d+e)
YZeq wfC C C ZwrC C C C C
where

F is the sum of the loads on the front wheels of the towing vehicle with the trailer attached and load-

ZwfC
distributing coupling engaged;

F is the sum of the loads on the rear wheels of the towing vehicle with the trailer attached and load-

ZwrC
distributing coupling engaged;
g is the gravitational constant;
m is the mass of the towing vehicle;
l is the wheelbase of the towing vehicle;
4 © ISO 2010 – All rights reserved
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ISO 9815:2010(E)

d is the longitudinal distance between the centre of gravity of the towing vehicle and the centreline

of the rear axle of the towing vehicle;

e is the rear overhang, the longitudinal distance between the spindle axis of the rear axle and the

centre of the coupling ball.
6 Test method
6.1 General
Prior to testing, the vehicle shall be warmed up,
...

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